This application claims the benefit of Korean Application No. 10152/1996 filed on Apr. 4, 1996, which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a liquid crystal display, and more particularly to an IPS(In-Plane Switching) liquid crystal display that is large in area and exhibits a wide viewing angle.
Conventional TFT LDCs (thin film transistor liquid crystal display) have a drawback known as a viewing angle dependency, that is, the contrast ratio is changed according to the viewing angle. This has made it difficult to apply the technology to a large size display.
To solve this problem, various liquid crystal displays have been proposed, such as a retardation attaching TNLCD (twisted nematic liquid crystal display) and a multi-domain liquid crystal display. The LCDs still have other technical problems such as complicated production process and shifting color tones.
2. Discussion of the Related Art
Recently, an IPS LCD has been introduced to obtain a wide viewing angle. This technology is discussed in JAPAN DISPLAY 92, p547, Japanese patent application No. 7-36058, Japanese patent application No. 7-225538, and ASIA DISPLAY 95, p707. As shown in FIG. 1a and FIG. 1c, in the liquid crystal layer 12 the molecules are aligned at a 45xc2x0 angle. The principal transmittance axis of a polarizer 9 attached to the first substrate 1 is the same direction as the alignment direction of the liquid crystal 12, and the principal transmittance direction of an analyzer 10 attached to the second substrate 5 is perpendicular to the alignment direction of the liquid crystal layer 12. A pair of electrodes 2, 3 is formed on the first substrate 1.
In FIG. 1b and FIG. 1d, when the voltage is applied between two electrodes, a horizontal electric field is created. Therefore, the transmittance is controlled by causing the liquid crystal molecules to be rotated to be parallel with the electric field. When the rotation angle of the liquid crystal molecules is 45xc2x0 in the normally black mode, the retardation value(xcex94nd) is about xcex/2(0.21-0.36 xcexcm) for a maximum transmittance.
In conventional IPS LCDs as described above, the transmittance is controlled by birefringence, and a retardation film is necessary to compensate for the viewing angle which increases the manufacturing cost.
In addition, a viewing angle inverted area appears in the central portion of the outer lines of the display.
Accordingly, the present invention is directed to a liquid crystal display that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is an IPS mode liquid crystal display having a wide viewing angle and improved picture quality.
Another object of the present invention is an IPS mode liquid crystal display that can be fabricated at low cost by using a low voltage driving IC and by eliminating the need for a retardation film.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the liquid crystal display device of the present invention includes a first substrate having a first surface and a second surface, a first alignment layer formed on the second surface of the first substrate, a second substrate having a first surface and a second surface, a second alignment layer formed on the second surface of the second substrate, a molecular liquid crystal layer between the second surface of the first substrate and the second surface of the second substrate, a pair of electrodes formed in parallel on the second surface of the first substrate, a polarizer formed on the first surface of the first substrate and having a transmittance axis, and an analyzer formed on the second surface of the second substrate and having a transmittance axis.